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• fftools/ffmpeg : replace MATCH_PER_STREAM_OPT(.., str, ..) with a function

  6 août 2024, par Anton Khirnov

  fftools/ffmpeg : replace MATCH_PER_STREAM_OPT(.., str, ..) with a function
  This has multiple advantages :
  
  * The macro has multiple parameters that often have similar or identical
  
    values, yet very different meanings (one is the name of the
  
    OptionsContext member where the parsed options are stored, the other
  
    the name of the variable into which the result is written) ; this
  
    change makes each of these explicit.
  * The macro returns on failure, which may cause leaks - this was the
  
    reason for adding MATCH_PER_STREAM_OPT_CLEAN(), also ost_add()
  
    currently leaks encoder_opts. The new function returns failure to its
  
    caller, which decides how to deal with it. While that adds a lot of
  
    error checks/forwards for now, those will be reduced in following
  
    commits.
  * new code is type- and const- correct
  Invocations of MATCH_PER_STREAM_OPT() with other types will be converted
  
  in following commits.
  

  • [DH] fftools/cmdutils.c
  • [DH] fftools/cmdutils.h
  • [DH] fftools/ffmpeg.h
  • [DH] fftools/ffmpeg_demux.c
  • [DH] fftools/ffmpeg_mux.h
  • [DH] fftools/ffmpeg_mux_init.c
  • [DH] fftools/ffmpeg_opt.c

• Parsing NAL units using FFMPEG

  6 novembre 2013, par 2ndlife

  I am new to MPEG-4 and taking baby steps to learn it. I am using FFMPEG as reference.

  1. I understand that all mpeg-4 are encoded into NAL units and wrt to FFMPEG av_read_frame() function returns one NAL unit, Am I right ? Is frame a NAL unit ? (though it can be a combination of multiple NALs)

  2. I also saw that h264_parser.c implements a function called h264_parse which is calling parse_nal_units() inside, If i need to get NAL units how can I use this parse_nal_units from my main function ?

  3. What is av_parse_Parse2() function do ? does it return decoded NAL units ?

  4. OR FFMPEG has -vbsf h264_mp4toannexb switch to dump raw NAL units, Can somebody help me understand how I can use the same from my main function ?

  Please help me out here...
   ash5

• Why does ffmpeg return "No such file or directory"

  4 juillet 2020, par JackNewman

  I'm trying to split a video file into 2 second increments and then merge the video back together.

  


  source_vid_path = r"C:\SplitAndMergeVids\Before\before.mp4"
ffcat_path = r'C:\SplitAndMergeVids\Chunk\video.ffcat'
chunks_path = r'C:\SplitAndMergeVids\Chunk\chunk-%03d.mp4'
segments_time = '2'
cmd_input = rf'ffmpeg -fflags +genpts -i {source_vid_path} -map 0 -c copy -f segment -segment_format mp4 -segment_time {segments_time} -segment_list {ffcat_path} -reset_timestamps 1 -v error {chunks_path}'
output = str(subprocess.run(cmd_input, shell=True, capture_output=True))
print(output)

output_path = r'C:\SplitAndMergeVids\Output\output.mp4'
second_input = rf'ffmpeg -y -v error -i {ffcat_path} -map 0 -c copy {output_path}'
output = str(subprocess.run(second_input, shell=True, capture_output=True))
print(output)


  


  First subprocess runs perfectly although the second outputs returns

  


  "Impossible to open 'chunk-000.mp4'\r\nC:\\SplitAndMergeVids\\Chunk\\video.ffcat: No such file or directory".


  


  Full output looks like

  


  CompletedProcess(args='ffmpeg -fflags +genpts -i C:\\SplitAndMergeVids\\Before\\before.mp4 -map 0 -c copy -f segment -segment_format mp4 -segment_time 2 -segment_list C:\\SplitAndMergeVids\\Chunk\\video.ffcat -reset_timestamps 1 -v error C:\\SplitAndMergeVids\\Chunk\\chunk-%03d.mp4', returncode=0, stdout=b'', stderr=b'')
CompletedProcess(args='ffmpeg -y -v error -i C:\\SplitAndMergeVids\\Chunk\\video.ffcat -map 0 -c copy C:\\SplitAndMergeVids\\Output\\output.mp4', returncode=1, stdout=b'', stderr=b"[concat @ 0000028691a6c6c0] Impossible to open 'chunk-000.mp4'\r\nC:\\SplitAndMergeVids\\Chunk\\video.ffcat: No such file or directory\r\n")


  


  When I run cmd_input and second_input manually in cmd, everything functions perfectly. I don't understand how in the first command I am making a file at "ffcat_path", then in the second command I'm using the same "ffcat_path" and it returns "No such file or directory" when it certainly does exist.